Field
Aspects of the present disclosure generally relate to an information processing apparatus including a nonvolatile main memory unit.
Description of the Related Art
Nonvolatile memories that allow a high speed read and write access have been in practical use. Such memories can be included in information processing apparatuses, such as personal computers, to serve as a main memory unit. Examples of a nonvolatile main memory unit include a magnetoresistive random access memory (MRAM), a ferroelectric random access memory (FeRAM), a resistance random access memory (ReRAM), and a phase change random access memory (PRAM).
Nonvolatile main memory units can continuously maintain data without continuous power supplied to the memory units. Accordingly, unlike information processing apparatuses including a volatile main memory unit, the power consumption of information processing apparatuses including a nonvolatile main memory unit is substantially zero when the information processing apparatus is in a suspended mode.
In addition, since the information processing apparatuses can retain a computer program in the nonvolatile main memory unit at all times, the information processing apparatuses need not load the computer program before executing the computer program. Thus, a start-up time of the information processing apparatuses can be reduced.
On the down side, it is difficult to prevent the stored information from leaking out of the information processing apparatus including a nonvolatile main memory unit.
That is, the information stored in the main memory unit is simply lost when power supplied to information processing apparatuses including a volatile main memory unit, such as a dynamic random access memory (DRAM), is stopped.
In contrast, even when power supplied to information processing apparatuses including a nonvolatile main memory unit is stopped, information stored in the main memory unit is continuously retained. Accordingly, after power supply is stopped, the main memory unit that retains the information can be physically removed from the information processing apparatus.
That is, information processing apparatuses including a nonvolatile main memory unit are at high risk of leaking information stored therein if the main memory unit is removed.
In particular, widely-used operating systems have a memory management mechanism to efficiently use the memory space. The processing performed by the memory management mechanism may cause leaking of the information. For example, the memory management mechanism of Linux™ may automatically copy data from one storage device to another storage device even when a user or a user program does not instruct the copying operation.
That is, even when the user does not explicitly instructs a computer, confidential information may be stored in the nonvolatile main memory unit.
To prevent the above-described leaking of information, the information stored in the main memory unit can be encrypted. Japanese Patent Laid-Open No. 2008-204507 describes a technology for preventing leaking of information out of an information processing apparatus including a RAM. According to the technology described in Japanese Patent Laid-Open No. 2008-204507, data encrypted using scramble information is stored in an MRAM. The encrypted data cannot be decrypted unless the key information for decryption is available.
On the down side, in the technology described in Japanese Patent Laid-Open No. 2008-204507, a mechanism for performing a scramble process and a descramble process is required. Accordingly, the data in the MRAM cannot be directly used and, thus, the processing speed of reading and writing data may decrease.
In addition, Japanese Patent Laid-Open No. 2012-168737 describes an information processing apparatus including a volatile memory unit and a nonvolatile memory unit to prevent leaking of information. More specifically, to prevent leaking of information, some of data are stored in the volatile memory unit. In this manner, although the data stored in the nonvolatile memory unit may be leaked out, all the data are not leaked out, since some of the data are stored in the volatile memory unit. According to the technology described in Japanese Patent Laid-Open No. 2012-168737, the data stored in the memory units are not encrypted. Accordingly, the processing speed negligibly decreases.
However, there is a risk of leaking out some of the data. That is, according to the technology described in Japanese Patent Laid-Open No. 2012-168737, the protection is not always perfect.